Technical Abstract:
Crossbreed steers (n = 20; 235 ± 4 kg) were fed 53 d during a receiving period to determine if supplementing chromium (Cr; KemTRACE®brand Chromium Propionate 0.04%, Kemin Industries) would alter the glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0 (Con) or 0.2 mg/kg of Cr to the total diet on a DM basis. Cattle were fitted with jugular catheters on d 52. A glucose tolerance test (GTT) and an insulin sensitivity test (IST) were conducted on d 53 by infusing the steers with 1 mL of a 50% glucose solution/kg of BW (Dextrose 50%, Durvet, Inc.) at 0900 h and 0.1 IU of a bovine insulin solution/kg of BW at 1400 h, respectfully. Blood samples were collected at -60, -45, -30, -15, 0, 7.5, 15, 30, 45, 60, 90, 120, and 150 min relative to each infusion. Serum was isolated to determine the glucose, insulin, and non-esterified fatty acid (NEFA) concentrations. Data were analyzed using the Mixed procedure of SAS specific for repeated measures with each steer serving as the experimental unit and fixed effects of treatment, time, and their interaction. Throughout the GTT no differences were detected in glucose concentrations or per-infusion insulin concentrations (P > 0.50), but insulin concentrations post-infusion tended to be higher for the Cr cattle (P = 0.06). In addition, NEFA concentration during the GTT were lower (P = 0.01) for Cr cattle both pre and post-infusion. During the IST there was no treatment effect on glucose concentrations pre-infusion (P = 0.38), but post-infusion glucose concentrations were higher (P < 0.01) in the Cr group. During the same test, there were no treatment effects detected for insulin concentrations (P > 0.33), but at 7.5 min there was a trend for the insulin concentrations of the control cattle to reach a higher peak (P = 0.12). Concentrations of NEFA were lower (P < 0.01) both pre and post-infusion during the IST. Results of this study indicate that supplementation of Cr to the basal diet can alter insulin sensitivity and lipid metabolism of newly received steers during the first 53 d on feed.